The invention covers an emergency brake for a rail car equipped with a brake shoe which operates in conjunction with a rail brake surface. Emergency brakes of this type are known as magnet rail brakes, as shown in German Patent No. 1,605,262. Magnet rail brakes require substantial controls, which is not felt so much when dealing with large cars, but which, however, causes relatively high costs for small cars.
It is the object of this invention to design suitable emergency brakes for small cars. This is solved by arranging on both sides of the brake tappet, parallel with the rail brake surface, a wedge-shaped brake shoe in such a way that the distance from the brake shoe to the rail brake surface next to the brake tappet is greater than at the outer ends, and that a brake antifriction body is provided between the brake tappet and the rail brake surface. The brake tappet is operated by a centrifugal governor.
When releasing the brake tappet by means of the centrifugal governor, the brake tappet moves the brake antifriction body against the rail brake surface. In accordance with the direction of motion of the rail car, the brake antifriction body rotates and moves between one of the tapered brake shoe extensions and the rail brake surface. If, for example, the rail car becomes defective while going uphill and the engine brake fails, it would then roll back towards the valley until the set value for maximum speed has been exceeded, so that the centrifugal governor frees the brake tappet. The brake antifriction body then rotates on the rail brake surface and moves between the wedge-shaped brake shoe on the uphill side and the rail brake surface.
If the rail car becomes defective while going downhill and the engine brake fails, the centrifugal governor, upon exceeding the limit set for maximum speed, releases the brake tappet which moves the brake antifriction body against the rail brake surface, where it wedges itself between the wedge-shaped brake shoe on the downhill side and the rail brake surface, thus stopping the rail car. The parts of the emergency brake are commercially available and, therefore, inexpensive.
Furthermore, the brake antifriction body is, in released brake position, held by a device coaxially in front of the brake tappet between the brake shoe ends, so that the brake antifriction body does not shift into one of the brake positions inadvertently. Such device consists, preferably, of a lock spring with lock cam protruding into an indentation in the brake antifriction body. The indentation is located on the longitudinal axis of the cylindrical brake antifriction body.
The brake antifriction body may be made of synthetic material or metal. If it is made of synthetic material, it may be provided with a covering of serrated spring steel. A brake antifriction body made of metal may have a covering of synthetic material. The brake antifriction body made of synthetics with a spring steel covering is advantageous, in that it does not clamp as jerkily as a brake antifriction body made of metal, which would lead to a jolting stop of the car and possibly injure passengers. If a brake antifriction body is deformed after a stop, or even destroyed, it may be replaced quickly.
In another feature of the invention, the brake tappet end facing the rail brake surface and adhering to the brake antifriction body may be beveled on both sides so that the brake antifriction body is pushed into operating direction after moving in front of the brake shoes. The brake tappet is charged by a tappet spring in the direction of the brake surface on the rail and adheres with a block at the bolt lever connected to the centrifugal governor and/or speed governor. The latter releases the bolt lever when exceeding the set speed.
The brake shoes are connected to a counterpressure surface arranged on the rail surface opposite the rail brake surface. This counterpressure surface acts as a brake surface as well, and prevents absorption of reaction forces directed laterally by the rail car, such forces occurring during the wedging process of the brake antifriction body. Brake shoes and counterpressure surface are located in a housing in which the brake tappet as well as the lock cam for the brake antifriction body are housed, also. The brake shoes are limited at their extreme ends for the brake antifriction body. The brake surfaces and the counterpressure surface are arranged within the housing displaceable vertically to the rail brake surface, and are held in a central position by guide springs absorbing tension and pressure. The guide springs prevent constant pendulum motion of brake surfaces and counterpressure surfaces within the housing. Together with the guide for brake surfaces and counterpressure surfaces, they facilitate the adjustment of these parts on the rail without the necessity of transmitting the motion to the entire car. Furthermore, the housing forms a simple construction and assembly unit for the emergency brake.
The centrifugal governor and/or speed governor already mentioned is a further feature of the invention, and consists of a disc with several centrifugal weights radially displaceable against the force of springs and, in their extreme position, causing the release of a bolt lever, thus releasing the brake tappet. The disc is connected via a shaft with a wheel running on the rail and is, thus, directly influenced by the running speed .